Cured fluorinated elastomer

ABSTRACT

A cured fluorinated elastomeric copolymer of vinylidene fluoride and at least one comonomer selected from the group consisting of chlorotrifluoroethylene, perfluoropropene and tetrafluoroethylene, said cured elastomer having a compression set below about 10 percent after 24 hours at 205° C. in ASTM D 395-61 method B and being prepared from a material having a Mooney 10 point rise at 120° C. above 25 minutes using ASTM D 1646-63 method with the small rotor.

This application is a continuation of U.S. application Ser. No. 3,396,filed Jan. 16, 1970 now U.S. Pat. No. 3,655,727, which is acontinuation-in-part application of U.S. application Ser. No. 831,295,filed June 9, 1969, now abandoned which is a continuation-in-part ofU.S. application Ser. No. 802,917, filed Feb. 27, 1969 now abandoned,which is a continuation-in-part application of U.S. application Ser. No.753,618, filed Aug. 19, 1968 now abandoned.

This invention relates to a method for crosslinking fluorinated polymersand crosslinking compositions for use therein. In one aspect thisinvention relates to a new vulcanization admixture for producing acrosslinked product of improved compression set. In another aspect thisinvention relates to the modification of the characteristics of linearsaturated polymers containing halogen substituents on the carbon atoms,particularly those polymers having elastomeric properties.

In general, linear polymers are thermoplastic in nature and exhibitcontinuous flow under the influence of heat and pressure. Such polymerscan be resoftened as often as desired and are usually soluble inselected solvents. However crosslinked or vulcanized polymers aregenerally thermoset, i.e. insoluble in most solvents and incapable ofbeing resoftened without decomposition, since they are permanentlyhardened. A linear polymer may nevertheless contain a small number ofcrosslinkages without losing its thermoplastic properties. It is oftendesirable to convert thermoplastic polymers into crosslinked polymers orinto partially crosslinked polymers in order to decrease theirsolubility and thermoplastic flow properties and to obtain a harder andtougher product. The crosslinking of elastomers is commonly referred toas vulcanization.

Among the most difficultly vulcanizable thermoplastic polymers are thoseprepared by the polymerization of halogenated monoolefins, such as, forexample, the copolymers of chlorotrifluoroethylene and vinylidenefluoride, the copolymers of perfluoropropene and vinylidene fluoride andthe terpolymers of perfluoropropene, vinylidene fluoride andtetrafluoroethylene. Many of these fluorinated thermoplastic polymershave unique and valuable properties. In some cases, when it is desiredto retain these properties and at the same time decrease thethermoplastic flow and solubility, the polymers are crosslinked. Suchcrosslinking has heretofore resulted in a relatively high compressionset of the final product, e.g. a compression set of more than 30% after24 hours at 400° F. (205° C.).

One major utility of vulcanized, highly fluorinated elastomers lies intheir use as gaskets, O-rings and the like, for containing fluids underpressure at elevated temperatures, as, for example, in hydraulic systemsin aircraft, or as components of reactors in the processing ofchemicals. In use, the elastomer is continually compressed for extendedperiods of time. If during use the elastomeric part becomes permanentlyperformed, i.e., undergoes compression set, the seal fails causingleakage. In general, the higher the temperature and the longer theelastomer is under compression, the greater the degree of compressionset and accordingly the greater the danger of equipment failure.

It is therefore an object of this invention to provide a new andimproved crosslinking system.

Another object of this invention is to provide a new curable,fluorinated polymer admixture.

Still another object of this invention is to provide a method forcrosslinking vulcanizable fluorinated elastomers.

A further object of this invention is to provide a cured fluorinatedelastomer with improved physical properties, including low compressionset.

An important object of this invention is to provide a crosslinking orcuring system for fluorinated elastomers which utilizes relatively lowconcentrations of curing agent but which still is capable ofconveniently producing a cured elastomer having low compression set andhaving a minimal amount of residual, unreacted curing agent, therebyreducing the undesirable tendency of the cured elastomer to further cureduring actual use, aging or testing.

Other objects and advantages of the present invention will becomeapparent to those skilled in the art from the accompanying descriptionand disclosure.

Accordingly the invention provides an elastomeric composition curable inreactive association with an inorganic acid acceptor capable ofgenerating water upon reacting with hydrogen fluoride to produce a curedelastomer having low compression set. The curable elastomericcomposition or admixture comprises the following components:

a. a fluorinated elastomeric copolymer of vinylidene fluoride and atleast one terminally unsaturated fluoromonoolefin containing at leastone fluorine atom substituent on each double bonded carbon atom, eachcarbon atom of said fluoromonoolefin being substituted only withfluorine, chlorine, hydrogen or a lower fluoroalkyl or fluoroalkoxyradical, at least 10 percent of the chain carbon atoms of said copolymerbeing --CH₂ -- units;

b. at least one quaternary ammonium or quaternary phosphonium compoundof the formula

    [R.sub.3.sup.1 Q--R.sup.2 --QR.sub.3.sup.3 ].sup.+.sup.2 [X.sup..sup.-m ].sub.2/m

or

    [R.sup.4 --Q--R.sub.3.sup.5 ].sup.+.sup.1 [X.sup..sup.-m ].sub.1/m

wherein Q is a phosphorus or nitrogen atom, X is an anion (e.g. sulfate,acetate, phosphate, halide, hydroxide, alkoxide, phenoxide, etc.), m isthe valence of anion X (e.g. 1-3), R² is an alkylene radical having from2 to 12 (preferably 2 to 6) carbon atoms or a phenylene dialkyleneradical having from 8 to 12 carbon atoms (e.g. --CH₂ --C₆ H₄ --CH₂ --),R--⁴ is an alkyl radical having from 1 to 12 (preferably 1 to 6) carbonatoms or an aralkyl radical having from 7 to 12 carbon atoms, andwherein R¹, R³ and R⁵ represent alkyl radicals having from 1 to 18(preferably 1 to 12, most preferably 1 to 6) carbon atoms;

c. at least one aromatic hydroxy or amino compound which has anoxidation potential no more than 1.5 volts with respect to a standardcalomel electrode; and

d. in a preferred embodiment the curable composition also includes atleast one compound which is stable in the absence of water attemperatures below about 75° C. and which at a temperature above 125° C.and in the presence of water releases a basic nitrogen-atom containingcompound having at least one hydrogen atom bonded to said basic nitrogenatom. Preferably the compound is one which releases a primary orsecondary amine, a hydrazine or ammonia.

Although the mechanism is not fully understood, the combination of eachof the above components in vulcanization system displays an effect notattributable to any one specific component or any combination less thanthe required components of the above curing system, resulting in adrastic reduction in the compression set of the cured product, i.e. lessthan 20 percent compression set and generally less than about 10 percentcompression set after exposure to 400° F. (205° C.) for 24 hours, andalso resulting in a complete cure with essentially no residual effectivecuring agent, all of which is accomplished with a low concentration ofcuring ingredients, as will be hereinafter discussed. Another valuableattribute of the above curing system is the greater latitude permissablein the formulation, and minor changes in the proportions of thecomponents within the specified limits do not drastically effect theprocessability, particularly its ability to be milled without scorchingand yet to cure rapidly.

The vulcanizable polymers which are cured according to this inventionare linear, saturated, fluorinated polymers which contain reactivesubstituents selected from the group consisting of hydrogen, fluorineand chlorine and which are at least half halogenated. By "halfhalogenated" is meant that at least one half of the carbon bondedhydrogen atoms of the analogous nonhalogenated polymer are replaced byhalogen. The preferred vulcanizable polymers are at least halffluorinated; however, it is critical that the polymer chain include--CH₂ -- units. Homopolymers of tetrafluoroethylene and otherperfluorinated olefins, and copolymers thereof with other perfluorinatedcomonomers require very high temperature to effect crosslinking and arenot within the scope of this invention.

Linear fluorinated elastomers generally contain disordered, saturated,fluorinated carbon chains which include a substantial number of --CH₂ --units, usually at least 10 percent of the chain carbon atoms. Disorderin the carbon chains is ordinarily achieved by the copolymerization ofat least two monoolefinic compounds of the type hereinafter described.When one of the monoolefinic compounds contains an unsaturated chain ofthree or more carbon atoms, alkyl side groups, e.g. methyl, ethyl, etc.,are present in the final polymer, and these alkyl groups are preferablyperhalogenated, most preferably perfluorinated. Points of unbalance inthe carbon chain, which are necessary for elastomeric properties, areprovided by these side groups. Such side groups cause a bending of thelinear carbon chain and thus provide additional degrees of freedom inspace, producing an unsymmetrical chain carbon atom to which they areattached. However, unbalance is also provided by the presence of otherunsymmetrical units in the linear carbon chain such as --CFCl--.Irrespective of the units providing such points of unbalance, whether bytwo physically different substituent atoms or by a side group on a chaincarbon atom, at least 10 percent of the chain carbon atoms should beunbalanced.

The linear, saturated, fluorinated carbon chain in the elastomers mayalso contain chlorine substituents, provided a single chain carbon atomhas no more than one chlorine attached thereto to produce instability orto influence the chemical nature of the elastomer. The presence of morethan one chlorine substituent on a single chain carbon atom produces apoint of rigidity in the chain, decreasing the flexibility of the chainand the elastomeric properties accordingly.

Among the saturated polymers which may be crosslinked in accordance withthis invention are the fluorinated elastomeric copolymers ofchlorotrifluoroethylene, vinylidene fluoride, 2-chloroperfluoropropene,a fluorinated methyl vinyl ether, perfluoropropene, tetrafluoroethylene,1-hydroperfluoropropene (i.e. CFH=CFCF₃), dichlorodifluoroethylene,trifluoroethylene, 1, 1-chlorofluoroethylene and vinylidene chloride.These monoolefins may be copolymerized with each other in groups of twoor more. They may also be copolymerized with other olefinic compoundssuch as ethylene. The preferred elastomers are copolymers of vinylidenefluoride with at least one terminally unsaturated fluoromonoolefincontaining at least one fluorine atoms substituent on each double bondedcarbon atom, each carbon atom of said fluoromonoolefin being substitutedonly with fluorine, chlorine, hydrogen or a lower fluoroalkyl (e.g.perfluoroalkyl) or fluoroalkoxy radical, particularly perfluoropropene,tetrafluoroethylene, chlorotrifluoroethylene and1-hydroperfluoropropene. Particularly preferred are the fluorinatedelastomers produced by copolymerizing perfluoropropene and vinylidenefluoride, as described in U.S. Pat. Nos. 3,051,677 issued Aug. 28, 1962and 3,318,854, issued May 9, 1967 and those terpolymers produced bycopolymerizing perfluoropropene, vinylidene fluoride andtetrafluoroethylene as described in U.S. Pat. No. 2,968,649 issued Jan.17, 1961. The elastomeric copolymers of perfluoropropene and vinylidenefluoride having between about 15 and about 50 mole percentperfluoropropene are outstanding in this respect.

A critical ingredient in the final curable composition is at least oneoxidizable aromatic hydroxy or amino compound which has an oxidationpotential no greater than 1.5 volt, preferably no greater than 1 volt,with respect to a standard saturated calomel electrode and which is freeof electron attracting groups as substituents on the aromatic nucleus.Oxidation potentials are conveniently measured by conventional cyclicvoltammetry, using a platinum electrode and the compounds atconcentrations of about 10.sup.⁻³ mol per liter in substantiallyanhydrous dimethylformamide, including 0.2 moles/liter of a solubleconductivity aid, such as sodium perchlorate. Among those compoundsoxidizing between about 1 and 1.5 volts in this test are phenol,meta-cresol, resorcinol, catechol, bis-phenol A [i.e. 2,2-bis(p-hydroxyphenyl) propane] and p-bromophenol. Among those compoundsoxidizing at no more than about 1 volt are p-dihydroxybenzene,o-dihydroxybenzene and pyrogallol. The preferred aromatic hydroxy oramino compounds are represented by the general formula:

    ArZ.sub.n

wherein Z represents an --OH or --NH₂ aromatic ring substituent, nrepresents an integer from 1 to 2, and Ar represents an n-valentaromatic nucleus (e.g. phenyl, naphthyl). Preferably the aromaticnucleus is unsubstituted, but it may also be substituted. Ifsubstituted, electron-donor groups such as alkyl, alkoxy, aryl aryloxy,and aralkyl are preferred, since electron attracting substituent groupssuch as halogen, nitro, carboxyl, and the like result in an aromaticcompound which, unless used with a more severe curing cycle, tends toproduce a cured elastomer with higher compression set. Hydroquinone,i.e. p-dihydroxybenzene, is a particularly preferred compound.

The composition also includes at least one quaternary ammonium orquaternary phosphonium compound of the formula recited earlier. Typicalquaternary ammonium compounds include:

    (CH.sub.3).sub.4 N.sup.+OH.sup.-, [(C.sub.4 H.sub.9).sub.4 N].sup.+[OH.sup.-],

    [(ch.sub.3).sub.3 nch.sub.2 c.sub.6 h.sub.5 ].sup.+[oh.sup.-],

    [(c.sub.4 h.sub.9).sub.3 nch.sub.2 ch.sub.2 n(c.sub.4 h.sub.9).sub.3 ].sup.+.sup.2 [oh.sup.-].sub.2,

    [(ch.sub.3).sub.3 nch.sub.2 c.sub.6 h.sub.4 ch.sub.2 n(ch.sub.3).sub.3 ].sup.+.sup.2 [oh.sup.-].sub.2

and the corresponding salts thereof, such as tetrabutylammonium bromide.Quaternary phosphonium compounds include, for example,

    [(C.sub.4 H.sub.9).sub.4 P.sup.+]Br.sup.-,

and ##STR1##

    [(CH.sub.3).sub.4 P.sup.+] [acetate.sup.-]

    [(C.sub.4 H.sub.9).sub.4 P.sup.+][OH.sup.-]

the quaternary compounds are conveniently admixed with thefluoroelastomer as a solution in an inert, volatile solvent, such asmethanol, although many of the compounds can also be introduced to thecurable elastomer in the form of finely divided solids. The salts ofthese quaternary compounds are generally preferred over thecorresponding hydroxides because of their better stability.

A further component in the final curing recipe is an inorganic acidacceptor capable of generating water upon reacting with hydrogenfluoride. Suitable acid acceptors are bases and include magnesium oxide,lead oxide (litharge, PbO), dibasic lead phosphite and zinc oxide, withmagnesium oxide being preferred. The acid acceptors are used in amountsranging from 2 to 25 parts per 100 parts of polymer. In addition an"optional base" is generally desired as a cure accelerator. Theseoptional bases are basic compounds and include inorganic oxides andhydroxides such as calcium hydroxide, barium carbonate, strontiumhydroxide, and the like. The optional bases are preferably used inamounts ranging from 0.5 to 10 parts per 100 parts of polymer.

Although not necessary, the composition preferably contains at least onearomatic amine (primary, secondary or tertiary), aliphatic tertiaryamine, or a compound which is stable in the absence of water attemperatures below about 75° C. and which at temperatures above about125° C. in the presence of water generates a basic nitrogenatom-containing compound (i.e a compound having a pK_(b) in water of nomore than about 14) having at least one hydrogen atom bonded to saidbasic nitrogen atom (preferably generates a primary or secondary amine,a hydrazine or ammonia), all of which will be referred to herein as"amines." Amines having too high a molecular weight diffuse lessefficiently through the fluorocarbon polymer during the curing process,thus tending to result in uneven cure and inferior physical propertiesof the resulting vulcanizate. Generally, a satisfactory cure can beobtained most effectively with an amine having a molecular weight of notmore than about 1000, and in most cases an amine having a molecularweight of not more than about 500 is preferred. In order to obtainoptimum physical properties, particularly resistance to changes duringaging and resistance to solvents, it is desirable that the amineequivalent weight (i.e. total molecular weight divided by the number ofbasic nitrogen atoms in the molecule) in the free amine should be nogreater than about 500, and preferably no greater than about 300.

For purposes of this discussion, compounds which generate a basicnitrogen atom-containing compound, while considered "amines" asmentioned above, will also be more particularly referred as "aminegenerators," the preferred amine generators being further characterizedas "amine adducts" or "carbonyl adducts." It is to be understood thatwhile the amine generators of this invention must be capable ofgenerating an amine in the presence of water, certain of the usefulamine generators are also capable of generating an amine in the presenceor absence of water, e.g. carbamates, urethanes, carbodiimides,thiourethanes, etc.

The mechanism of curing saturated copolymers of vinylidene fluoridewith, for example, perfluoropropene, is not fully understood. Existingevidence suggests that the initial press cure involves a base-catalyzedrelease of hydrogen fluoride to generate double bonds in the polymer,these double bonds then providing a limited number of crosslinks betweenthe polymer chains which serve to stabilize the shape and form of thepolymer, while the subsequent postcure step results in the formation offurther ethylenically unsaturated structures which combine to formbenzenoid crosslinks of high thermostability. This is consistent withour findings that a variety of compositions function as curing orcrosslinking agents, acting to aid in the release of hydrogen fluoride.Most free primary or secondary aliphatic amines (insofar as they are notin themselves amine generators), free hydrazine or free ammonia are notsuitable as curing agents, and their use as such results in either toorapid a cure rate or no cure at all.

It is convenient to consider the preferred carbonyl adduct as derivedfrom the reaction of a carbonyl compound and an amine, and in most casesthe adduct may be prepared in this manner. However, carbonyl adductswithin the scope of this invention may also be prepared by alternativesyntheses which are chemically equivalent. Carbonyl adducts whichthermally or upon reaction with one or more molecules of water generatethe same amine act in the formulation as equivalents. For examplehexylisocyanate and hexane carbodiimide as well as hexylcarbamate,N-hexylacetamide are considered herein as equivalent carbonyl adducts ofhexylamine and either carbon dioxide or acetic acid, since they liberatethe same amine, as is shown by the following reactions:

    ______________________________________                                        [C.sub.6 H.sub.13 NHCO.sub.2 ].sup.-[C.sub.6 H.sub.13 NH.sub.3 ].sup.+                          2C.sub.6 H.sub.13 NH.sub.2 + CO.sub.2                       C.sub.6 H.sub.13 N=C=HC.sub.6 H.sub.13 + 2H.sub.2 O                                             2C.sub.6 H.sub.13 NH.sub.2 + CO.sub.2                       C.sub.6 H.sub.13 NCO + H.sub.2 O                                                                C.sub.6 H.sub.13 NH.sub.2 + CO.sub.2                        (C.sub.6 H.sub.13 NCO).sub.2 + 2H.sub.2 O                                                       2C.sub.6 H.sub.13 NH.sub.2 + 2CO.sub.2                      CH.sub.3 CONHC.sub.6 H.sub.13 + H.sub.2 O                                                       C.sub.6 H.sub.13 NH.sub.2 + CH.sub.3 CO.sub.2 H             ______________________________________                                         (C.sub.6 H.sub.13 NH).sub.3 P=O is not an equivalent carbonyl adduct of     hexylamine, since it does not liberate a carbonyl derivative, but is     regarded as a useful amine generator because it generates a suitable     amine.

The carbonyl moiety of the carbonyl adduct is generally derivable fromcarbon dioxide, carboxylic (including polycarboxylic) acids, aldehydesor ketones. The preferred aldehydes and ketones and carboxylic acids arerepresented by the general structural formulae: R₂ ⁶ C=O; R⁶ (COOH)₁ ₋₄; wherein R⁶ represents hydrogen, an alkyl (including cycloalkyl)radical of 1 to 25 (preferably 1 to 12) carbon atoms, an aralkyl radicalof 7 to 25 carbon atoms, or an aryl (including alkaryl) radical of 6 to25 carbon atoms. Two alkyl radicals may be combined to form an alicyclicdivalent radical, e.g. cyclohexanone, ##STR2## Exemplary adductsinclude: 1. Aldehyde - ammonia adducts, e.g., ##STR3## 2. Aldehyde -primary amine adducts, e.g.,

    R.sup.6 CH=O + H.sub.2 NR.sup.7 → R.sup.6 CH=NR.sup.7 + H.sub.2 O

3. aldehyde - secondary amine adducts, e.g.,

    R.sub.2.sup.6 CHCH=O + HNR.sup.7 R.sup.8 → R.sub.2.sup.6 C=CHNR.sup.7 R.sup.8 + H.sub.2 O

4. ketone - primary amine adducts, e.g.,

    R.sub.2.sup.7 C=O + H.sub.2 NR.sup.7 → R.sub.2.sup.7 C=NR.sup.7 + H.sub.2 O

5. ketone - secondary amine adducts, e.g.,

    R.sub.2.sup.6 CHCOR.sup.7 + HNR.sup.7 R.sup.8 → R.sub.2.sup.6 C=CR.sup.7 NR.sup.7 R.sup.8 + H.sub.2 O

6.

    co.sub.2 + 2h.sub.2 nr.sup.7 → [r.sup.7 nhco.sub.2 .sup.-][r.sup.7 nh.sub.3 .sup.+]

in the above formula R⁶ is as defined earlier; R⁷ and R⁸ may be selectedindependently from the group consisting of aromatic radicals of 6 to 25(preferably 6 to 12) carbon atoms, unsubstituted, saturated aliphaticradicals of 1 to 25 (preferably 1 to 18, most preferably 1 to 6) carbonatoms (e.g., alkyl and cycloalkyl) and araliphatic radicals of 7 to 25(preferably 7 to 12) carbon atoms.

While the above illustrations exemplify monoamino compounds, polyamino(including diamino) compounds are equally useful and in some casespreferred. For example, in place of ammonia, hydrazine (H₂ N--NH₂) canbe used; in place of hexylamine, H₂ N--(CH₂)₅ CH₃, hexamethylenediamine,H₂ N(CH₂)₅ CH₂ NH₂, can be used; in place of C₆ H₅ NHC₁₈ H₃₇, C₆ H₅NHC₃₆ H₇₂ NHC₆ H₅ can be used, and so on. At least one of the aminogroups is combined in the form of a carbonyl adduct, but alternativelymore than one, or all, may be so combined. For simplicity andconvenience, a symmetrical compound is preferred, but an unsymmetricalcompound, such as 6-methylaminohexylamine, is equally suitable.

It should be noted that aldehyde and ketone compounds, to react with asecondary amine in the preparation of a carbonyl adduct, must have atleast one hydrogen substituent on at least one carbon atom adjacent tothe carbonyl carbon. Carbon-bonded substituents such as hydroxyl orhalogen, (e.g., chlorine or fluorine) generally interfere neither withthe formation of carbonyl adducts nor with the ability of such adductsto function as curing agents.

The most preferred amine generators of this invention are eitherdialdehyde aliphatic diamine adducts (i.e. dialdimine) of the generalformula:

    R.sup.7 --CH=(CH--CH=).sub.m N(C.sub.n H.sub.2n)N(=CH--CH).sub.m =CHR.sup.7

wherein R⁷ is as defined above, m is 0 or 1 and n is 2 to 36, preferably2 to 6; or a carbamate of the general formula:

    YHN--C.sub.n H.sub.2n --X

wherein Y is a hydrogen atom, an alkyl radical of 1 to 6 carbon atoms oran aryl radical of 6 to 12 carbon atoms (preferably Y is a hydrogenatom), X is a carbamic radical, and n is 2 to 36, preferably 2 to 6.

The amine generator may be incorporated directly into the elastomericmaterial to be cured or, in the case of carbonyl adducts, the respectivecomponents or precursors thereof may be introduced into the curableelastomeric material when their reaction in situ occurs to form thedesired amine adduct, for example, during the milling or mixing of therubber formulation prior to cure.

A particularly useful amine generator of the present invention iscinnamylidenetrimethylenediamine. The most preferred amine generatorsare produced in known manner by reaction of an aliphatic orcycloaliphatic diamine with an aldehyde or with carbon dioxide.Illustrative adducts of the diamine with carbon dioxide (i.e.carbamates) are shown in U.S. Pat. No. 3,096,314 and described inconjunction with the curing of highly fluorinated elastomers.

The following are examples of aldehyde-diamine adducts useful in thepractice of the invention as well as the aldehydes and amines from whichthey are produced.

    __________________________________________________________________________    Aldehydes     Amines     Adducts                                              __________________________________________________________________________     ##STR4##      H.sub.2 NCH.sub.2 CH.sub.2 NH.sub.2                                                      ##STR5##                                             ##STR6##      H.sub.2 (CH.sub.2).sub.3 NH.sub.2                                                        ##STR7##                                             ##STR8##      H.sub.2 N(CH.sub.2).sub.3 NH.sub.2                                                       ##STR9##                                             ##STR10##     H.sub.2 NCH(CH.sub.3)CH.sub.2 NH.sub.2                                                   ##STR11##                                            ##STR12##     H.sub.2 N(CH.sub.2).sub.2 NH.sub.2                                                       ##STR13##                                            ##STR14##     H.sub.2 N(CH.sub.2).sub.3 NH.sub.2                                                       ##STR15##                                            ##STR16##     H.sub.2 N(CH.sub.2).sub.2 NH.sub.2                                                       ##STR17##                                           __________________________________________________________________________

Other useful amine generators include complexes of amines withtransition elements, such as nickel, iron and cobalt (as illustrated bythe complexes prepared by reacting three moles of ethylenediamine withone mole of nickel or cobalt acetate in alcohol solution) and alsoinclude complexes of metal such as silver and zinc. Compounds equivalentto the amines, such as triphenylstibine, triphenylbismuthine,triphenylarsine, dibutyl tin sulfide and tributylphosphine, may also beemployed in similar fashion as the "amine."

The quaternary compound, alone or premixed with a suitable a may beconveniently milled into the elastomer gum stock. Thus mixed, the stockcan be stored at room temperature (i.e. about 80° F. or 27° C.) forextended periods, e.g. at least six months. Prior to curing, theoxidizable aromatic hydroxy or amino compound and the acid acceptors aremilled into the stock, after which the storage life at ambienttemperatures is more limited and molding or extruding the product withinabout two to three weeks is recommended. Of course, all of thecomponents of the curing system may be admixed prior to theirincorporation into the elastomer without departing from the scope ofthis invention. It may also be desirable in some instances to employretarding agents, plasticizers, fillers, and other conventionaladditives.

The proportions of components of the curing system are set forth belowin parts by weight. (All amounts referred to herein are in parts per 100parts of polymer abbreviated "pphr," unless otherwise indicated.) Theseproportions are general ranges and the particular amount for eachparticular cure, time and temperature will become apparent to thoseskilled in the art.

                  TABLE I                                                         ______________________________________                                        Formulation Limits                                                            Component            Parts phr (range)                                        Amine                0 - 2.5                                                                       (preferably 0.1-2.5)                                     Quaternary compound  0.05 - 0.5                                               Acid Acceptor        2 - 25                                                   Optional Base        0 - 10                                                   Oxidizable hydroxy or amino compound                                                               0.1 - 2                                                  ______________________________________                                    

Although low compression set elastomers are obtained within theaforementioned formulation limits, elastomeric products havingcompression set values of 10 or less may be obtained by varying therelative amounts of the components listed in Table I within thespecified ranges. Preferably the quaternary ammonium or phosphoniumcompounds are added in solution in a solvent such as methanol.

Use of larger amounts of amine tends to increase the cure rates andprovide a tighter cure. However, excessive amounts may promote excessivecuring on aging and to effect, for example, higher compression setvalues and lower elongation values. Generally, when an amine is used,the lowest amount of amine which will provide the desired rate of cureand level of compression set at practical curing temperatures ispreferred and, in fact, amounts much in excess of about 2.5 pphr areundesirable because of the adverse effect on heat aging properties.

Quaternary ammonium and phosphonium compounds, when used in amounts assmall as 0.05 pphr, produce a measurable acceleratory effect on curerate at a given amine concentration. An excess of the quaternarycompound, over 0.4 pphr, particularly when more than about 0.5 pphr,tends to effect an overcured vulcanizate, although in general the highermolecular weight quaternary compound can be used in greater amounts thanthose of lower molecular weights. Generally, the lower the amount ofamine employed, the greater the optimum amount of the quaternarycompound. The preferred proportions in an exemplary system usingtetrabutylammonium hydroxide and cinnamylidene trimethylenediamine areillustrated in the drawings, and are represented by the shaded area ofthe graph. The following equation describes these preferred proportions:

    x± 0.1 = 0.3 (1-y/2)

wherein x is the amount of hydroxide in pphr, y is the amount of aminein pphr, x being greater than or equal to 0.05 and y being greater thanor equal to 0.25.

Of the acid acceptors, magnesium oxide is preferred. At least about 2pphr is required to provide a reasonable level of cure and rate of cure.The maximum amount for the acid acceptor as listed in Table I is notcritical, as much as 50 to 60 pphr producing a usable but hard stock.Generally, however, no more than about 25 parts is necessary foradequate curing. Alternatively, zinc oxide, litharge or dibasic leadphosphite may be used in approximately the same proportions, and calciumoxide may sometimes be used.

In addition to the above acid acceptor, when an optional base is desiredas an accelerator, it is usually present in amounts of from about 0.5 to10.0 pphr. Calcium hydroxide is preferred, barium carbonate being milderand generally being used in somewhat larger amounts.

Fillers are often added to the polymers discussed above to improve themolding characteristics and other properties. When a filler is employedit is added to the vulcanization recipe in amounts of up to about 100parts pphr, preferably between about 15 and about 50 parts. Examples offillers which may be used are reinforcing thermal grade carbon blacks ornon-black pigments of relatively low reinforcement characteristics suchas clays, barytes, etc. Plasticizers, softeners and processing aids,preferably esters or ketones, may also be added if desired.

In accordance with this invention, the desired amount of the componentsof the crosslinking system is added to the unvulcanized fluorocarbonpolymer (i.e. gum stock) and is intimately admixed therewith orcompounded by employing any of the usual rubber mixing devices, such asBanbury mixers, roll mills, or any other convenient mixing device. Ithas been found that a two-roll rubber mill equipped with heat exchangemeans, e.g. cored chambers for cooling, is particularly suitable sincethe heat generated by the high shearing forces in mixing can bedissipated and the temperature more accurately regulated with thisdevice or with devices providing other means for temperature control.

For best results the temperature of the mixture on the mill is notallowed to rise above about 250° F. (120° C.) and is not allowed to fallbelow 30° F. (0° C.). During milling it is necessary to distribute thecrosslinking agent uniformly throughout the curable polymer. However, itis also desirable to prevent extensive crosslinking in the compoundingstep since most of these fluorinated polymers cannot be molded orextruded after a substantial amount of crosslinking has taken place.

The curing process typically comprises pressing the compounded mixturein a mold and then baking the pressing in an oven. Pressing of thecompounded mixture (press cure) is conducted at a temperature betweenabout 200° F. (95° C.) and about 450° F. (230° C.), preferably betweenabout 300° F. (150° C.) and about 400° F. (205° C.) for a period of from1 minute to about 15 hours, usually from 5 minutes to 30 minutes. Apressure of between about 7 and about 210, preferably between about 35and about 70, kg/cm² is imposed on the compounded mixture in the mold.The molds may be first coated with release agents, such as a siliconeoil, and prebaked. The molded vulcanizate is then usually post cured(oven cured) at a temperature between about 300° F. (150° C.) and about600° F. (315° C.), usually at about 400° F. (205° C.) for a period offrom 2 hours or less to 50 hours depending on the cross-sectionalthickness of the sample. The temperature during the post cure is usuallyraised gradually from the lower limit of the range to the desiredmaximum temperature selected. The maximum temperature used is preferablyabout 500° F. (260° C.) and is held at this value for at least 24 hours.

The following examples are offered as a better understanding of thepresent invention and are not to be unnecessarily construed as limitingthe scope thereof. In the examples, indicated results were obtainedusing the following test methods:

    __________________________________________________________________________    Mooney Scorch  ASTM D 1646-63 using the small                                                rotor                                                          Compression Set                                                                              ASTM D 395-61 method B using a                                                1" (25 mm) diameter × .5" (12.5                                         mm) thick sample compressed to                                                0.375" (9.5 mm) for the indicated                                             time at the indicated temperature.                                            One half hour was allowed after                                               the release of pressure for                                                   relaxation and temperature and                                                equilibration                                                  Tensile Strength at Break                                                                    ASTM D 412-62T on a sample cut                                                from 0.07" (1.8 mm) sheet with a                               Elongation at Break                                                                          die having the following dimensions:                           Modulus at 100% Elongation                                                                   A = 0.125" (3.5 mm)                                                           L = 0.75" (19 mm)                                                             C = 2.0" (51 mm)                                               Accelerated Aging                                                                            ASTM D 573-53 exposed for 16                                                  hours at 600° F. (315° C.)                       Press Cure     Unless otherwise noted sheets                                                 were prepared 3" × 6" × 0.07"                                     (75 × 150 × 1.8 mm) pressed at                                    about 1,000 psi (70 kg/cm.sup.2) for                                          20 minutes at 320°  F. (160° C.) for                            physical property determinations;                                             plugs for compression set were 1"                                             (25 mm) diameter × 0.5" (12.5 mm)                                       thick, pressed at about 2,000 psi                                             (140 kg/cm.sup.2) for 30 minutes at                                           320° F. (160° C.)                                Post Cure      Samples were removed from the                                                 press and placed in a circulating                                             air oven. The oven was maintained                                             at 300° F. (150° C.) for 2 hours,                               increased to 350° F. (175° C.) and                              held for 2 hours, increased to                                                400° F. (205° C.) and held for 20                               hours, then increased to 500° F.                                       (260° C.) and held for 24 hours.                                       (unless otherwise noted, see Ex.IX-XII)                        __________________________________________________________________________

EXAMPLE I

The interrelated effects on rate of cure, physical properties andstability toward aging due to variations in amounts of amine, quaternarycompound, oxidizable aromatic hydroxy or amino compound, and optionalbase are demonstrated by the results of the tests indicated in Table A.

The data in Table A illustrate the value of using an amine together witha quaternary compound and an oxidizable aromatic hydroxy compound. Run Ishows the results obtained with the omission of the quaternary compound,and Runs II - V show results obtained with varying amounts of thequaternary compound in the formulation of this invention. In Run I thecompression set is significantly higher than in Runs II - V. Inaddition, the higher level of amine required in Run I produces muchpoorer aging, as represented by greatly decreased elongation at break,greatly increased hardness, and an inability to obtain a 100 percentmodulus because of the very low elongation due to aging after post cure.This aging is an indication of the manner in which the cured elastomerwill function during actual use.

                                      TABLE A                                     __________________________________________________________________________    Run                   I        II       III  IV       V                       __________________________________________________________________________    Elastomer (C.sub.3 F.sub.6 /CF.sub.2 =CH.sub.2, 24/76 mole                                          100io)   100      100  100      100                     MgO                   10       10       10   10       10                      Carbon black          20       20       20   20       20                      Cinnamylidenetrimethylenediamine                                                                    2        0.7      0.3  0.5      0.5                     Tetrabutyl ammonium hydroxide                                                                       --       0.1      0.3  0.2      0.2                     Hydroquinone          1        0.5      2    2        1                       Ca(OH).sub.2          1        3        1    1        1                       CaS                   0.5      --       --   0.5      0.5                     Mooney 10 pt. rise at                                                                    250° F. (120° C.)                                                          >25 min. >25 min. --   >25 min  >25 min.                           330° F. (165° C.)                                                          3.0      2.5      --   6.5      6.0                     Compression set                                                                       1 day at 400° F. (205° C.)                                                    10       7        4.5  6        6                               7 days at 400° F. (205° C.)                                                   32       24       --   18       14                              7 days at 347° F. (175° C.)                                                   18       12       --   7        9                               3 days at 77° F. (25° C.)                                                     7        5        --   3        6                       Tensile at Break, psi (kg/cm.sup.2)                                                          A*     2120 (148)                                                                             1870 (132)    2075 (145)                                                                             2015 (140)                             B**    650  ( 45)                                                                             540  (38)     520  (36)                                                                              420  (29)               Elongation at Break (%)                                                                      A      220      260           270      330                                    B      80       180           160      220                     Hardness, Shore A.sub.2                                                                      A      71       69            70       68                                     B      78       69            71       68                      Modulus at 100% Elongation                                                                   A      220  (15)                                                                              455  (32)     475  (33)                                                                              320  (22)                              B      Broke    415  (29)     370  (26)                                                                              260  (18)               __________________________________________________________________________      *A - data from post-cured sample                                             **B - data from post-cured sample after accelerated aging (i.e. 16 hours      at 316° C.)                                                       

In Example 1 of U.S. Pat. No. 2,951,832 a formulation using a diamineadduct both along and in combination with a diamine carbamate producescured fluorinated elastomers which, after 70 hours at only 250° F. (120°C.) have compression set values of 30

to 60%. From the compression set data in Table A of the present Example,a reduction in the temperature from 400° F. (205° C.) to 350° F. (175°C.) results in a decrease of compression set of from 14-24% to 9-12%,and a further decrease of the temperature to 250° F. (120° C.) wouldclearly still further decrease the compression set values. Thisillustrates the significant improvement in compression set of the curingformulations of the present invention.

EXAMPLE II

The effect on cure results of varying the amount of hydroquinone wasobserved using a formulation having the following components and theamounts of hydroquinone noted in Table B:

    ______________________________________                                        Elastomer (C.sub.3 F.sub.6 /CF.sub.2 =CH.sub.2, 24/76 mole                                             100io   parts                                        MgO                      10      pphr                                         Carbon black             20      pphr                                         Ca(OH).sub.2             1       pphr                                         Cinnamylidenetrimethylenediamine                                                                       0.5     pphr                                         Tetrabutylammonium hydroxide                                                                           0.2     pphr                                         CaS                      0.5     pphr                                         ______________________________________                                    

                  TABLE B                                                         ______________________________________                                              Hydroquinone              Cure                                          Sample                                                                              (pphr)     Cure Conditions                                                                              Results                                       ______________________________________                                        1     0          320° F. (160° C.),                                                             Blown                                                           20 minutes                                                  2     0          395° F. (200° C.),                                                             No Cure                                                         5 minutes                                                   3     0.25       320° F. (160° C.),                                                             Good                                                            20 minutes                                                  4     0.5        320° F. (160° C.),                                                             Good                                                            20 minutes                                                  5     0.5        395° F. (200° C.),                                                             Good                                                            5 minutes                                                   6     1.0        395° F. (200° C.),                                                             Good                                                            5 minutes                                                   7     2.0        395° F. (200° C.),                                                             Good                                                            5 minutes                                                   ______________________________________                                    

At 0.1 pphr hydroquinone slightly increased amounts of diamine adduct,tetrabutylammonium hydroxide and/or calcium hydroxide are required toobtain acceptable cure results.

EXAMPLE III

Using the following formulation:

    ______________________________________                                        Elastomer (C.sub.3 F.sub.6 /CF.sub.2 =CH.sub.2, 24/76 mole                                             100io)  parts                                        MgO                      10      pphr                                         Carbon black             20      pphr                                         Ca(OH).sub.2             1       pphr                                         CaS                      0.5     pphr                                         Hydroquinone             2       pphr                                         ______________________________________                                    

Several samples were prepared with varying amounts ofhexamethylenediaminecarbamate, containing 0.5, 1.0 and 1.5 parts byweight respectively. Each sample was subjected to a press cure as inExample 1 for 30 minutes at 325° F. (165° C.). In none of the sampleswas a cure obtained. These samples indicate the need for the quaternaryammonium hydroxide to effect a satisfactory cure in ahydroquinone-containing system for the production of a rubber havinggood physical properties, including low compression set.

EXAMPLE IV

This experiment shows the effect using various diamine adducts in astandard formulation consisting of:

    ______________________________________                                        Elastomer (C.sub.3 F.sub.6 /CF.sub.2 =CH.sub.2, 24/76 mole                                             100io)  parts                                        Carbon black             20      pphr                                         MgO                      10      pphr                                         Ca(OH).sub.2             1       pphr                                         Tetrabutylammonium hydroxide                                                                           0.2     pphr                                         Hydroquinone             1       pphr                                         ______________________________________                                    

The adducts were added in approximately equimolar quantities, thecompounded stock milled, molded and post-cured as in Example I, andproperties determined as follows:

    __________________________________________________________________________    Cinnamylidene-                                                                              0.5 pphr                                                                            --      --    --     --                                     ethylenediamine                                                             Cinnamylidene-                                                                                --  0.5 pphr                                                                              --    --     --                                     trimethylenediamine                                                         Cinnamylidene-                                                                                --    --  0.6 pphr                                                                              --     --                                     hexamethylenediamine                                                        Trimethylenediamine-                                                                          --    --    --  0.25 pphr                                                                              --                                     carbamate                                                                   Hexamethylenediamine-                                                                         --    --    --    --   0.25 pphr                                carbamate                                                                   Mooney, 10 point rise at                                                        167° C., minutes                                                                   4.7   4.5   3.4   4.2    3.5                                    Compression Set, %                                                              1 day at 205° C.                                                                   6     6     5     7      6                                      Tensile Strength at                                                                         2040  2360  2000  2080   2100                                     break, psi (kg/cm.sup.2)                                                                  (142) (165) (140) (146)  (147)                                    A                                                                           Tensile Strength at                                                             break, psi (kg/cm.sup.2)                                                                  580   560   710   630    550                                      B           (41)  (39)  (50)  (44)   (38)                                   100% Modulus, psi                                                             (kg/cm.sup.2)A                                                                              450   510   720   380    420                                                  (31)  (36)  (50)  (27)   (39)                                   100% Modulus, psi                                                                           580     --    --  460      --                                   (kg/cm.sup.2) B                                                                             (41)              (32)                                          Elongation at Break,                                                          % A           240   200   220   260    210                                    Elongation at Break,                                                                        100   90    90    160    95                                     % B                                                                           Shore A.sub.2 Hardness, A                                                                   70    70    70    71     70                                     Shore A.sub.2 Hardness, B                                                                   75    71    73    70     74                                     __________________________________________________________________________     A data from post-cured sample                                                 B data from post-cured after accelerated aging                           

EXAMPLE V

To illustrate the equivalence of various aldehyde adducts, mixtures wereprepared according to the formulation in Table B except thathydroquinone was maintained at 1 pphr and various dialdehyde adducts oftrimethylenediamine were used each at 0.5 pphr. The materials weremolded and post-cured. The compression set data are shown in Table C.

                                      TABLE C                                     __________________________________________________________________________                          Compression Set %                                       Adduct                1 day at 205° C.                                                                 7 days at 175° C.                      __________________________________________________________________________     ##STR18##            6         7                                              ##STR19##            5         6                                              ##STR20##            4         4                                              ##STR21##            cracked   6                                              ##STR22##                                                                    __________________________________________________________________________                          5         5                                         

EXAMPLE VI

The effect of various readily oxidized aromatic amines and phenols isshown in Table D.

A standard formulation was prepared from:

    ______________________________________                                        Elastomer (C.sub.3 F.sub.6 /CF.sub.2 =CH.sub.2, 24/76 mole                                             100io)  parts                                        Carbon black             20      pphr                                         MgO                      10      pphr                                         Ca(OH).sub.2             1       pphr                                         Tetrabutylammonium hydroxide                                                                           0.2     pphr                                         Cinnamylidenetrimethylenediamine                                                                       0.5     pphr                                         Aromatic compound        1       pphr                                         ______________________________________                                    

The materials were milled to a uniform dispersion, then sheets and plugsprepared as described above. Sheets were press cured for 20 minutes at335° F. (165° C.) and plugs for 30 minutes at 320° F. (160° C.), thenpost cured and tested. The pertinent results are summarized in Table D.

                                      TABLE D                                     __________________________________________________________________________    Aromatic  Compression                                                                          Tensile  100% Modulus                                                                            Elongation**                              Compound  Set %* Psi  Kg/cm.sup.2                                                                       Psi  Kg/cm.sup.2                                                                        %                                         __________________________________________________________________________    Phenol    15     1,880                                                                              132 410  29   270                                       o-dihydroxy-                                                                            16     2,000                                                                              140 340  24   270                                       benzene                                                                       m-dihydroxy-                                                                            12     2,050                                                                              144 440  31   230                                       benzene                                                                       p-dihydroxy-                                                                             6     2,360                                                                              165 510  36   200                                       benzene                                                                       m-methyl  13     2,560                                                                              179 750  52   260                                       phenol                                                                        p-methyl  13     2,600                                                                              182 610  43   230                                       phenol                                                                        m-amino   10     2,530                                                                              177 1,605                                                                              112  140                                       phenol                                                                        m-phenylene-                                                                            14     2,170                                                                              152 950  66   190                                       diamine                                                                       p-phenylene-                                                                            12     2,500                                                                              175 1,280                                                                              90   180                                       diamine                                                                       2,2 bis(p-hydr-                                                                         11     2,240                                                                              157 460  32   250                                       oxyphenyl)                                                                    propane                                                                       p-Br phenol***                                                                          19     2,500                                                                              175 370  26   320                                       __________________________________________________________________________     *24 hours at 400° F. (205° C.)                                  **Elongation at break                                                         ***Formulation includes 3 pphr Ca(OH).sub.2                              

Aromatic hydroxy and amino compounds containing an electronattractinggroup (e.g. p--Br phenol) generally require either larger amounts ofoptional base to provide a satisfactory cure under standard curingconditions, or more prolonged or higher temperature press cure.

EXAMPLE VII

This example compares the results obtained through use of a variety ofamine carbonyl adducts.

A base formulation was prepared consisting of:

    ______________________________________                                        Elastomer (C.sub.3 F.sub.6 /CF.sub.2 =CH.sub.2, 24/76 mole                                             100io)  parts                                        Carbon black             20      pphr                                         MgO                      10      pphr                                         Ca(OH).sub.2             1       pphr                                         Tetrabutylammonium hydroxide                                                                           0.2     pphr                                         Hydroquinone             1       pphr                                         ______________________________________                                    

This formulation, with the addition of the amount of amine generatorindicated in Table E, were milled to a uniform dispersion and samplesprepared as indicated in Example I. The pertinent test results aresummarized in Table E. The amines liberated by the corresponding aminegenerators of Table E are set forth in Table F.

EXAMPLE VIII

This example demonstrates the properties obtained when the followingelastomeric copolymer is employed: an elastomeric copolymer consistingof CFH=CFCF₃ /CH₂ =CF₂ in a mole ratio of 20/80 having a specificgravity of 1.816 at 25° C. and a Mooney Viscosity (ML 1 + 4, 100° C.) of90, available under the trade name Tecnoflon-T from Montecatini Edison,S.p.A., Milan, Italy.

A formulation is prepared consisting of:

    ______________________________________                                        Elastomer (C.sub.3 F.sub.5 H/CF.sub.2 =CH.sub.2, 20/80 mole                                           100io) parts                                          Carbon black            20     pphr                                           MgO                     10     pphr                                           Ca(OH).sub.2            2      pphr                                           Tetrabutylammonium hydroxide                                                                          0.2    pphr                                           Cinnamylidenetrimethylenediamine                                                                      0.5    pphr                                           Hydroquinone            1      pphr                                           ______________________________________                                    

The formulation was milled and cured as in Example VI. The followingproperties were determined:

    ______________________________________                                        Compression Set, [24 hours at 400° F.                                                               18 %                                             (205° C.)]                                                             Tensile             3070 psi (215 kg/cm.sup.2)                                100% Modulus        1070 psi ( 75 kg/cm.sup.2)                                Elongation at Break          190 %                                            Hardness, Shore A            70                                               ______________________________________                                    

                                      TABLE E                                     __________________________________________________________________________                           Amount                                                                             Compression*                                                                         Tensile  100% Modulus                                                                             Elongation**           Run   Amine Generator  pphr set, % psi  kg/cm.sup.2                                                                       psi  kg/cm.sup.2                                                                         %                      __________________________________________________________________________    1     cyclohexylamine  0.25        no cure                                    2     2-OH-ethylamine  0.25        no cure                                    3     cinnamylidene    0.5  11     2,510                                                                              175 440  31    260                           cyclohexylamine                                                        4     cinnamylidene    0.5  8      2,305                                                                              161 965  68    150                           aniline                                                                5     cinnamylidene    0.5  8      2,620                                                                              183 1,080                                                                              76    170                           o-NO.sub.2 aniline                                                            ##STR23##       0.5  8      2,740                                                                              192 650  46    230                    7                                                                                    ##STR24##       0.5  8      2,900                                                                              202 430  30    300                    8                                                                                    ##STR25##       0.75 7      2,860                                                                              200 880  62    190                    9                                                                                    ##STR26##       0.25 7      2,475                                                                              173 630  44    220                    10                                                                                   ##STR27##       0.25 7      2,900                                                                              202 520  36    300                    11    cinnamylidene    0.25 10     2,500                                                                              175 660  46    240                           methylamine                                                            12    cinnamylidene 2-OH-                                                                            0.5  7      2,280                                                                              159 415  29    250                           ethylamine                                                             13    cinnamylidene-2- 0.5  6      2,160                                                                              151 455  32    200                           methoxyethylamine                                                      14    cinnamylidene trimethylene                                                                     0.5  7      2,250                                                                              157 1,400                                                                              98    140                           diamine                                                                15                                                                                   ##STR28##       0.5  6      1,915                                                                              134 1,270                                                                              89    170                    16                                                                                   ##STR29##       0.5  6      2,200                                                                              154 1,140                                                                              80    170                    17    C.sub.2 H.sub.5 C(CH.sub.3)NNHC.sub.6 H.sub.5                                                  0.5  8      2,710                                                                              189 1,085                                                                              76    160                    18    isophthalyl hydrazide                                                                          0.5  8      2,290                                                                              160 780  55    190                    19    dimethyl glyoxime                                                                              0.2  12     2,375                                                                              166 940  66    170                    20    OCNC.sub.36 H.sub.68 NCO                                                                       1.0  9      2,400                                                                              168 1,450                                                                              100   140                    21    C.sub.18 H.sub.37 NCO                                                                          0.5  11     2,500                                                                              175 1,650                                                                              114   140                    __________________________________________________________________________     *  After 24 hours at 250° C.                                           ** Elongation at break                                                        *** As piperidine salt                                                        **** As a cyclohexylamine salt                                           

TABLE F

The following is a list of the amines liberated by the correspondingamine generators of Table E followed by molecular weight and amineequivalent weights.

    ______________________________________                                                             Molecular Amine Equiv-                                   Run  Amine           Weight    alent Weight                                   ______________________________________                                        1    cyclohexylamine 99        99                                             2    2-OH-ethylamine 61        61                                             3    cyclohexylamine 99        99                                             4    aniline         93        93                                             5    o-NO.sub.2 -aniline                                                                           138       138                                            6    cyclohexylamine 99        99                                             7    cyclohexylamine 99        99                                             8    cyclohexylamine 99        99                                             9    piperidine      85        85                                             10   cyclohexylamine 99        99                                             11   methylamine     31        31                                             12   2-OH-ethylamine 61        61                                             13   2-methoxyethylamine                                                                           75        75                                             14   trimethylene diamine                                                                          74        37                                             15   trimethylene diamine                                                                          74        37                                             16   trimethylene diamine                                                                          74        37                                             17   C.sub.6 H.sub.5 NHNH.sub.2                                                                    108       54                                             18   hydrazine       32        16                                             19   hydroxylamine   33        33                                             20   H.sub.2 NC.sub.36 H.sub.68 NH.sub.2                                                           532       266                                            21   C.sub.18 H.sub.37 NH.sub.2                                                                    269       269                                            ______________________________________                                    

EXAMPLE IX

The data in Table G shows the use of hydroquinone and various quaternarycompounds in a curable formulation containing no amine compounds. Lowcompression set values were obtained as reported. The amounts of thecomponents in the formulation are given in parts by weight, and thequaternary components were used in about 25 percent solution inmethanol.

EXAMPLE X

The need for both a quaternary compound and an oxidizable aromatichydroxy or amino compound is illustrated by the comparative data inTable H. All amounts are in parts by weight, and the quaternary compoundwas used in a 25 percent methanol solution. It is significant thatquaternary compounds at the relatively low concentrations of thisinvention do not effect a cure when no oxidizable aromatic hydroxy oramino compound is present. The use of large amounts of curing agent(e.g. quaternary compound) to obtain reasonable cure rates, as is shownin U.S. Pat. No. 3,403,127, is undesirable because of high compressionset and poor aging properties. Quantities are in parts by weight.

EXAMPLE XI

The data of Table I illustrate the poor results obtained when nooxidizable hydroxy or amino compound is included in the formulation. Nocure was obtained when only 1 part of the quaternary compound was used,and the cure obtained at the higher concentration of quaternary compoundresulted in a product with 44 percent compression set. Runs 1 and 2 ofTable I correspond to Examples 1(b) and 1(c) in U.S. Pat. No. 3,403,127.

EXAMPLE XII

The data in Table J exemplify the use of several quaternary phosphoniumcompounds. All concentrations are in parts by weight, and thephosphonium compounds were in 25 percent methanol solution. Each run wasmilled on a rubber mill, molded for 30 minutes at 335° F. and post curedat 500° F. for 20 hours.

EXAMPLE XIII

Runs illustrating the use of various amine compounds, including aromaticamines and tertiary amines, in the curable formulation along with thequaternary compound and oxidizable aromatic amino or hydroxy compound,are presented in Table K. The quaternary compound was in a 25 percentmethanol solution. All concentrations are in parts by weight.

                                      TABLE G                                     __________________________________________________________________________                                1      2      3      4      5                     __________________________________________________________________________    Fluoroelastomer (C.sub.3 F.sub.6 /CF.sub.2 CH.sub.2,24/76 mol                                             100io) 100    100    100    100                   [(C.sub.4 H.sub.9).sub.4 N.sup.+][OCH.sub.3 .sup.-]                                                       0.4                                               [(C.sub.4 H.sub.9).sub.4 N.sup.+][OC.sub.6 H.sub.5 .sup.-]                                                       0.5                                        [(C.sub.4 H.sub.9).sub.4 N.sup.+][OH.sup.-]                                                                             0.4                                  ##STR30##                                       0.5                          [(C.sub.4 H.sub.9).sub.4 N.sup.+][Br.sup.-]             0.5                   carbon black                30     30     30     30     30                    magnesium oxide             10     10     10     10     10                    Ca(OH).sub.2                2      2      2      2      2                     hydroquinone                1      1      1      1      1                     Cure: sheet - 168° C. (30 minutes)                                     plug - 160° C. (30 minutes)                                            Post cure: 260° C. (20 hours)                                          Compression Set (%)         7      7.4    11     6.3    8                      400° F. (205° C.), 22 hours                                    Mooney (10 pt rise at 121° C.), minutes                                                            25+    25+    1.4    25+    25+                   (point rise in 25 minutes at 121°  C.) 4                                                           0      --     4      2                            Mooney, 335° F. (168° C.)                                                                   3.9    5.4    0.3    3.0    4.7                   15 minute                                                                     30 minute                   4.5    6.1    0.4    3.3    5.4                   Original                                                                      Tensile at break (psi)      2025   2105   1480   2000   2130                  Modulus at 100% elongation (psi)                                                                          1430   1325   1300   1445   1000                  Elongation at break (%)     135    145    150    140    175                   Hardness, Shore A.sub.2     71     72     72     73     72                    Heat Aged (275° C., 72 hours)                                          Tensile at break (psi)      1410   1445   1400   1620   1490                  Modulus at 100% elongation (psi)                                                                          1345   --     --     1620   1380                  Elongation at break (%)     115    90     90     100    120                   Hardness, Shore A.sub.2     83     81     84     80     79                    __________________________________________________________________________

                  TABLE H                                                         ______________________________________                                                            1    2       3                                            ______________________________________                                        Elastomer(C.sub.3 F.sub.6 /CF.sub.2 =CH.sub.2,24/76 mol                                             100io) 100     100                                      tetrabutylammonium bromide                                                                          0.5    0.5                                              hydroquinone          1.0            1.0                                      carbon black          30     30      30                                       magnesium oxide       10     10      10                                       calcium hydroxide     2      2       2                                         Cure: sheets - 168° C. (30 minutes)                                     plugs - 160° C. (30 minutes)                                          Post Cure:  260° C. (20 hours)                                        Compression set, %    6      NO      NO                                        205° C., 22 hours    CURE    CURE                                     Mooney                                                                          10 pt. rise at 121° C., minutes                                                            25+                                                       point rise in 25 minutes at 121° C.                                                        1                                                       Mooney, 335° F. (168° C.)                                         15 minute           4.4                                                       30 minute           5.1                                                     Original                                                                        Tensile at break (psi)                                                                            2000                                                      Modulus at 100% elongation (psi)                                                                  1245                                                      Elongation at break (%)                                                                           140                                                       Hardness, Shore A.sub.2                                                                           71                                                      Heat Aged (275° C., 72 hours)                                            Tensile at break (psi)                                                                            1385                                                      Elongation at break (%)                                                                           95                                                        Hardness, Shore A.sub.2                                                                           81                                                      ______________________________________                                    

                  TABLE I                                                         ______________________________________                                                             1      2                                                 ______________________________________                                         Vinylidene Fluoride/hexafluoropropene                                                               100      100                                             copolymer ("Vitron A")                                                      carbon black           20       20                                            magnesium oxide        15       15                                            calcium oxide          1        2                                             1,4-phenylene dimethylene bis-                                                                       1        2                                               (triethylammonium) chloride                                                 Cure: sheets -- 168° C., 45 minutes                                          plugs   -- 160° C., 45 minutes                                   Oven Cure:                                                                             100° C.(1hr), 120° C.(1hr), 140° C.(1hr),                160° C.(1hr), 180° C.(1hr), 200° C.(19hr)       Mooney, 335° F.(168° C.)                                          15 minute            13.7     6.5                                             30 minute            22+      9.8                                           Compression Set, %     No       44%                                             205° C., 24 hrs                                                      Original               CURE                                                    Tensile at break (psi)         1725                                           Modulus at 100% elongation (psi)                                                                    IN       745                                            Elongation at break(%)         200                                            Hardness, Shore A.sub.2                                                                             SHEET    69                                            Heat Aged (275° C., 72 hours)                                           Tensile at break (psi)                                                                              OR       1300                                           Elongation at break (%)        45                                             Hardness, Shore A.sub.2                                                                             PLUG     88                                            ______________________________________                                    

                  TABLE J                                                         ______________________________________                                        Cure and Post Cure as in Table C                                              ______________________________________                                                                 1    2                                               ______________________________________                                        Fluoroelastomer (C.sub.3 F.sub.6 /CF.sub.2 CH.sub.2 ;24/76 mol                                           100io) 100                                         [(C.sub.4 H.sub.9).sub.4 P.sup.+][Br.sup.-]                                                              0.53   --                                           ##STR31##                 --     0.58                                        carbon black               30     30                                          magnesium oxide            10     10                                          hydroquinone               1      1                                           calcium hydroxide          2      2                                           Compression Set (%)        6.5%   4.2%                                         at 400° F. (24 hr)                                                    Original                                                                       Tensile a break (psi)     2004   2140                                         Modulus at 100% elongation (psi)                                                                        1170   800                                          Elongation at break (%)   160    190                                          Hardness, Shore A.sub.2   73     70                                          Heat Aged (528° F., 72 hr)                                              Tensile at break (psi)    1360   1355                                         Modulus at 100% elongation (psi)                                                                        1180   765                                          Elongation at break (%)   135    190                                          Hardness, Shore A.sub.2   79     73                                          Mooney                                                                         10 pt. rise at 121° C., minutes                                                                  25+    25+                                         Mooney, 335° F.                                                         15 minute                 4.6    7.7                                          30 minute                 5.2    8.75                                        ______________________________________                                    

                                      TABLE K                                     __________________________________________________________________________                    1           2     3      4        5       6                   __________________________________________________________________________    Amine                                                                                          ##STR32##                                                                                 ##STR33##                                                                           ##STR34##                                                                            ##STR35##                                                                              ##STR36##                                                                            N(C.sub.2                                                                     H.sub.5).sub.3      C.sub.3 F.sub.6 /CF.sub.2 CH.sub.2 elastomer                                                  100         100   100    100      100     100                 (24/76 mol ratio)                                                             Weight of amine 0.5         0.5   0.5    0.5      0.5     0.5                 tetrabutylammonium hydroxide                                                                  0.2         0.2   0.2    0.2      0.2     0.2                 carbon black    30          30    30     30       30      30                  magnesium oxide 10          10    10     10       10      10                  hydroquinone    1           1     1      1        1       1                   calcium hydroxide                                                                             2           2     2      2        2       2                   Compression Set (%)                                                                           9           8.5   7      8.5      14      8                   (400° F., 24 hr)                                                       Original                                                                      Tensile at break (psi)                                                                        2535        2345  2330   2640     2010    2560                Modulus at 100% elongation (psi)                                                              2270        1600  1620   575      --      700                 Elongation at break (%)                                                                       120         135   140    230      60      210                 Hardness, Shore A.sub.2                                                                       77          69    70     65       80      65                  Heat Aged (72 hr at 528° F.)                                           Tensile at break (psi)                                                                        2030        1710  1700   1770     1355    1700                Modulus at 100% elongation (psi)                                                              1930        1260  1430   710      --      705                 Elongation at break (%)                                                                       110         140   130    190      20      250                 Hardness, Shore A.sub.2                                                                       80          72    76     68       94      68                  __________________________________________________________________________

What is claimed is:
 1. A cured fluorinated elastomeric copolymerconsisting essentially of vinylidene fluoride, perfluoropropene andtetrafluoroethylene in which the vinylidene fluoride content issufficient to provide at least 20 percent of the chain carbon atoms,said cured elastomer having a compression set below about 10 percentafter 24 hours at 205° C. in ASTM D 395-61 method B and being preparedfrom a material having a Mooney 10 point rise at 120° C. above 25minutes using ASTM D 1646-63 method with the small rotor.